http://www.hometheaterforum.com/htforum/showthread.php?s=&threadid=39997&highlight=htf+jazz+club
Cole Porter is, IMO, the most solid Ella songbook. The Berlin is pretty much as good. I personally love the Ellington book the most, but that's 'cause I'm a huge Ellington fan. The only book I'm not that thrilled about is the Gershwin, because I just don't like a lot of their songs. I love Porgy & Bess, but there are no songs from that work on the Gershwin songbook because she did a whole P&B album with Louis Armstrong.
For other vocals, there's Sarah Vaughan (her s/t is excellent) and Billie Holiday (there are many compilations of her early stuff which is, IMO, her best). These three sing in very different styles, and should give you and idea of what kind of singers you like. I can't recommend any male singers because I don't like any.
Some non-vocal albums that are universally considered great intros to jazz:
Dave Brubeck: Time Out
Miles Davis: Kind of Blue, Birth of the Cool, Cookin', Round About Midnight
John Coltrane: My Favorite Things
Sonny Rollins: Saxophone Colossus, Way Out West
Charlie Parker: Yardbird Suite (for a good intro on real be-bop)
Others I think are pretty nifty:
Thelonious Monk: pretty much all of it, very consistent stuff here
Mingus: Ah Um, Blues & Roots, Tijuana Moods (full disclosure: Mingus is my greatest musical hero)
Clifford Brown: Study in Brown (or any of those collections)
Note: my musical biases tend towards non-vocal modern jazz. But for pre-bop stuff, there are a lot of comps of Basie, Duke, Goodman, et al worth checking out as well.